1. Field of the Invention
The present invention relates to pressure transducers and more specifically to a capacitive pressure transducer of the type having a flexible diaphragm.
2. Description of the Prior Art
Rapid advances in the microelectronics art are making it feasible to employ microprocessors in digital control systems for mobile hydraulic equipment. An impediment to the commercialization of such digitally controlled hydraulic systems is the prohibitive cost of rugged and accurate sensors which are compatible with the harsh environmental conditions in which many hydraulic systems must operate.
A typical prior art capacitive pressure transducer includes a fixed metal plate and a diaphragm fabricated from a resilient metal which is mounted in front of the fixed plate inside a relatively rigid housing. The combination of the diaphragm and the fixed metal plate form the plates of a capacitor. When pressure is applied to the diaphragm, it bends closer to the fixed plate, thereby increasing the capacitance between the diaphragm and the fixed plate. When the pressure is removed or decreased, the resilience of the metal diaphragm causes it to return to its original position thereby decreasing the capacitance. The output signal of the transducer is a capacitance which varies as a function of the pressure change. The operating characteristics of the above described capactive pressure transducer are not sufficiently reliable for use in mobile hydraulic systems subject to a harsh environment and which require considerable accuracy.